Jpn. Pat. Appln. KOKOKU Publication No. 3598341 discloses a commodity management apparatus for managing the kind, remaining amount, etc. of a chemical contained in a chemical bottle in accordance with data in a wireless tag attached to the bottle and in accordance with the weight of the bottle. This apparatus includes an electronic weighing scale for weighing the chemical bottle mounted on a weighing dish, and a wireless tag reader/writer for contactlessly reading the data in the wireless tag attached to the chemical bottle using an antenna.
In this apparatus, the antenna for the wireless tag reader/writer is provided in the weighing dish of the electronic weighing scale. The antenna has directivity in a direction perpendicular to the surface of the weighing dish.
A passive wireless tag is attached to the chemical bottle. The passive wireless tag does not have its own power source. The passive wireless tag generally has a coil antenna, and generates electricity when a great amount of radio waves traverses the surface of the coil antenna. When the wireless tag generates electricity, the wireless tag reader/writer can read the data in the wireless tag.
Therefore, in this apparatus, the wireless tag has to be attached to the bottom surface of the chemical bottle so that a great amount of radio waves emitted from the antenna traverses the surface of the coil antenna of the wireless tag. If the wireless tag is affixed to some part other than the bottom surface, the efficiency of reading the wireless tag is significantly reduced.
However, the bottom of a container is not necessarily hollow. The wireless tag has its own thickness. Therefore, when the wireless tag is attached to the bottom surface of the container, the wireless tag may project from the bottom surface of the container. If the wireless tag projects from the bottom surface of the container, the container is not stable when mounted on the weighing dish, and may fall down while being weighed. Moreover, when the container is placed on, for example, a shelf or a table, the wireless tag is in contact with the mounting surface, so that the wireless tag tends to deteriorate. If the mounting surface is wet, the deterioration of the wireless tag accelerates.
Furthermore, in this apparatus, the antenna is provided in the weighing dish of the electronic weighing scale. In general, the scale requires the leveling of the weighing dish and a zero adjustment. However, such adjustments are difficult when the antenna is provided in the weighing dish, which is impractical.